Dating archaeological mortar by OSL is one of the challenging objectives leading to the chronology of ancient constructions. Single grain OSL analysis is a very convenient tool to examine the bleaching ... [more ▼]

Dating archaeological mortar by OSL is one of the challenging objectives leading to the chronology of ancient constructions. Single grain OSL analysis is a very convenient tool to examine the bleaching state of the series of quartz grains extracted from a mortar sample. Indeed, during the making process, sand is extracted from a sedimentary source, transported, stored then mixed with lime and set into the walls being constructed. Experience shows that incomplete bleaching is frequent for these materials. The aim of this study is to model the distribution of single grain equivalent doses of mortars following the assumption that a population of grains corresponds to a unique distribution of heterogeneously bleached grains rather than to a mixture of well bleached quartz grains with poorly bleached ones. An exponential distribution of light exposure of grains is examined. By comparing experimental distributions of doses with simulated ones, we investigate the appropriateness of this distribution function and then we calculate the average residual dose integrated into the process of the ED determination and finally the OSL age. Limits and potentials of this approach are discussed using various case-studies of structures and buildings of known age (from the roman to the post-medieval period). Even in case of very poorly bleached samples we observed that the simulated ED distribution fits satisfactorily with the experimental one, which offers new encouraging perspectives in single grain dating of mortars. [less ▲]

This study focuses on early medieval buildings in England and in France, specifically on those displaying the presence of brick in their masonry. The purpose was to determine whether medieval builders ... [more ▼]

This study focuses on early medieval buildings in England and in France, specifically on those displaying the presence of brick in their masonry. The purpose was to determine whether medieval builders reused Roman salvaged building materials or if the bricks used were contemporary to the building under construction. Thus luminescence dating was applied to bricks sampled from 11 standing Anglo-Saxon or Carolingian churches. The luminescence dates show that the two types of practice were in use in both countries. Where contemporary brickmaking appears to be the case, the study also provided a more precise chronology of the buildings. [less ▲]

The church of Saint-Irénée in Lyons, the capital city of the Gauls, is one of the oldest witnesses of Christianization, and it also attests to the evolution of Lyons under the aegis of the Burgundians ... [more ▼]

The church of Saint-Irénée in Lyons, the capital city of the Gauls, is one of the oldest witnesses of Christianization, and it also attests to the evolution of Lyons under the aegis of the Burgundians. New archaeological and historical data and a luminescence dating campaign presented here have renewed the previously held views on the development of the church of Saint-Irénée through the first centuries of its existence. Three main building stages were detected and the two first within a very short time span. According to the new data, the first building stage would have occurred between the 5th century and the beginning of the 6th century, the second one between the beginning of the 6th century and the beginning of the 7th century and the third one could be around the 9th-10th century period. Furthermore, we noticed that reused Gallo-Roman bricks were frequently set into the masonries which were studied in conjunction with the early medieval bricks that were specially produced for the (re)building stages already mentioned, which was unexpected. [less ▲]

vailable archaeomagnetic data indicate that during the past 2500 yr there have been periods of rapid geomagnetic field intensity fluctuations interspersed with periods of almost constant field strength ... [more ▼]

vailable archaeomagnetic data indicate that during the past 2500 yr there have been periods of rapid geomagnetic field intensity fluctuations interspersed with periods of almost constant field strength. Despite Europe being the most widely covered region in terms of archaeomagnetic data the occurrence and the behaviour of these rapid geomagnetic field intensity changes is under discussion and the challenge now is to precisely describe them. The aim of this study is to obtain an improved description of the sharp intensity change that took place in western Europe around 800 AD as well as to investigate if this peak is observed at the continental scale. For this purpose 13 precisely dated early medieval Spanish pottery fragments, four archaeological French kilns and three collections of bricks used for the construction of different French historical buildings with ages ranging between 335 and 1260 AD have been studied. Classical Thellier experiments performed on 164 specimens, and including anisotropy of thermoremanent magnetisation and cooling rate corrections, gave 119 reliable results. The 10 new high-quality mean archaeointensities obtained confirm the existence of an intensity maximum of ∼85 μT (at the latitude of Paris) centred at ∼800 AD and suggest that a previous abrupt intensity change occurred around 600 AD. Together with previously published data from western Europe that we deem to be the most reliable, the new data also suggest the existence of two other abrupt geomagnetic field intensity variations during the 12th century and around the second half of the 13th century AD. High-quality archaeointensities available from eastern Europe indicate that very similar geomagnetic field intensity changes occurred in this region. European data indicate that very rapid intensity changes (of at least 20 μT/century) took place in the recent history of the Earth's magnetic field. The results call for additional high-quality archaeointensities obtained from precisely dated samples and for a selection of the previously published data if a refined description of geomagnetic field intensity changes at regional scales is to be obtained. [less ▲]